Taxonomical use of floral scent data in apomictic taxa of Hieracium and Sorbus derived from hybridization

Scent investigations are mainly carried out in the context of the ecological function of scent components for pollinator attraction, to study their geographical variability or their evolution. In contrast, profiles of inflorescence scent compounds were rarely used for phylogenetic analyses and taxonomy. So far no investigations are available that focus on scent of apomictic plant groups and its value for the taxonomy of these groups. Apomicts produce fertile seeds without pollination. Overall, apomixis occurs scattered over the whole Angiosperm tree in early as well as late branching families. Rosaceae and Asteraceae are particularly rich in apomictic taxa. In these families genera such as Hieracium and Sorbus contribute a lot to local species biodiversity in Central Europe because of their high number of apomictic species and taxa, which are often endemic. Most members of these genera built up polyploid microspecies swarms initiated by hybridization events. The reticulate structure of these taxon complexes leads to taxonomic difficulties that can not be solved by morphology alone. Therefore, molecular or chemical markers are needed to investigate the parentage of such taxa and their collective species membership. An important starting point of this research was the finding that artificial hybrids of Citrus produce a combination of the leaf and peel volatiles of their parents. This led to the hypothesis that natural hybrids might likewise produce scent patterns combined of the volatiles of their parents. Inflorescence scents were investigated from 64 mainly Bavarian taxa of the genus Hieracium (Subgenus Pilosella and Subgenus Hieracium). In Sorbus (Rosaceae) we focussed on three taxa of the S. latifolia agg., endemic to Northern Bavaria, S. adeana, S. cordigastensis and S. franconica and their parental species from the S. aria aggregate (agg.), as well as S. torminalis. Samples were collected with dynamic headspace method. Substances were identified by gas chromatography coupled to mass spectrometry (GC-MS). Scent data were evaluated by using various cluster methods. In Hieracium, additional reticulation analyses were applied that trace conflicting signals in a phylogram which can be interpreted as hybridizations between the taxa involved. In Sorbus additional AFLP (Amplified Fragment Length Polymorphism) analyses were carried out from the populations and individuals that were studied for scent and genetic and scent data were correlated. In Hieracium, the inflorescense scent consisted mainly of sesquiterpenes, monoterpenes, aliphatics and aromatics. In the flower scent of Sorbus besides these substances also nitrogene-containing substances were found. In Hieracium (both subgenera) as well as in Sorbus, taxa of hybrid origin showed a mixed scent pattern compared with the parental taxa. In many cases, the parental taxa that had been suggested by morphological investigations or revealed by genetic investigations could be confirmed by scent. In general, scent patterns correlate well with morphological or genetical groupings, both in Hieracium and in Sorbus. Reticulate scent analyses in Hieracium showed that some taxa are probably derived from more than two ancestors. Scent data reflected even taxonomic patterns on a higher level, i.e. the sectional level. The AFLP study revealed that the selected members of the Sorbus latifolia agg. are genetically clearly differentiated and mostly of clonal structure. They are more closely related to S. aria than to S. torminalis. The S. aria agg. has a complex structure. Besides S. aria s.str. and S. pannonica there are also intermediate plants with affinity (aff.) to either the one or the other of these taxa. S. cordigastensis was derived from intermediates aff. S. aria s.str., and both S. adeana and S. franconica derived from intermediates aff. S. pannonica or S. pannonica itself. Floral scent of the same Sorbus taxa was investigated and compared with AFLP data on individual as well as on population level. Correlation analysis revealed a very high correlation between scent and AFLP data on individual and population level. Overall, this work shows that in two unrelated plant complexes, Hieracium and Sorbus, which both harbour a high number of apomictic species derived by hybridization, scent is of high taxonomical value. The main reason for this correlation may be that most taxa in the investigated groups possess mixed scent patterns from their parents or progenitors because they are of hybrid origin. In addition, intraspecific variability of scent patterns is low within apomictic taxa due to their clonality, simplifying the taxonomic use of scent data. Furthermore, the role of pollinator mediated selection of scent is reduced because of apomixis.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Bayreuth

Year

2013

Author dc:creator

• Feulner, Martin

Contributors dc:contributor

• Liede-Schumann, Sigrid

Repository record source_url

https://epub.uni-bayreuth.de/id/eprint/91/

OAI identifier oai:identifier

oai:epub.uni-bayreuth.de:91